Effective work function tuning in high-kappa dielectric metal-oxide-semiconductor stacks by fluorine and lanthanide doping

In this letter, an ion implantation approach to engineer the effective work function is discussed and an empirical model to explain the mechanisms of work function change is proposed. It is shown that by doping a TiN/HfSiOx stack with La and F, a silicon conduction band edge and valence band edge metal effective work function of 3.8 and 5.4 eV, respectively, can be achieved. The empirical correlation of the achieved effective work function to the electronegativity of the dopant element is explained.